Search for the H-Dibaryon near ΛΛ threshold at J-PARC

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1 Workshop on New Hadrons, Pusan, November 19-21, 2012 Search for the H-Dibaryon near ΛΛ threshold at J-PARC Jung Keun Ahn (Pusan National University)

2 H-Dibaryon A.T.M. Aerts and C.B. Dover, PRD28 (1983) 450 Theoretical Estimate RD K. Yamamoto et al (E885), PLB478 (2000) 401

3 H(2250) H-Dibaryon as a ΛΛ Resonance?

4 H-Dibaryon from Lattice QCD Recent LQCD calculations seem to point to a weekly bound H or resonant state although we have got to wait for definite results with physical quark masses. with respect to K mass HAL Collab., PRL 106 (2011) / NP LQCD Collab. PRL 106 (2011) Shanahan, Thomas, Young, PRL 107 (2011)

5 Bound, Virtual State (a= ), or Resonance? Schaffner-Bielich (2012) Weakly-bound : H Λpπ weak decay Virtual state : ΛΛ threshold effect Resonance : Breit-Wigner peak in the ΛΛ mass spectrum.

6 ΛΛ Theoretical and Experimental Recent Results from STAR Only small fraction of ΛΛ or ΞN pairs will be produced close enough in space and with their relative momenta small enough to interact via H-formation.

7 Λpπ Theoretical and Experimental Recent Results from STAR and ALICE Rotational background?

8 ΛΛ Production in (K-,K+) Reaction Theoretical prediction by Aerts and Dover for K-(pp) K+H on 3 He (~0.2 μb/sr) KEK-E224 measurement for 12 C(K-,K+)ΛΛX (7.6 μb/sr and 3 μb/sr for the H)

9 Recent effective-lagrangian model calculation s- and u-channels via Y* for Ξ production R. Shyam et al, arxiv Ξp H fusion (Aerts and Dover PRD28 (1983) 450)

10 Lineshape of ΛΛ mass spectrum and ΛΛ scattering length.

11 The H-dibaryon (E42) To confirm whether or not the previously observed enhancement is due to the H-dibaryon with much higher statistics and much precise mass resolution. (K-,K+) reaction on a C(diamond) target with p=1.8 GeV/c K- beam at J-PARC. Large acceptance for ΛΛ detection near the target (a Helmholtz-type dipole magnet with a TPC and trigger counters). Detecting Σ-p, Λpπ, ΛΛ, and Ξ-p systems.

12 The E42 Collaboration

13 E42 J-PARC K1.8 Theoretical and Experimental Hyperon Spectrometer + K + Spectrometer Superconducting Helmholtz-type magnet Time Projection Chamber

14 Time Projection Chamber ~5000 pads 2.5x9 mm 2, 2.5x13 mm 2 Field cage TPC pad configuration TPC FEEs using A-GET chips

15 Magnetic Field Strengths calculated using OPERA-3D Return Yoke KURAMA Helmholtz

16 Yield Estimation from E224 data (PLB444 (1998)) ΛΛ events for 100 shifts and 1440 H(2250) events for 1.0 μb/sr with a 15-mm thick diamond target.

17 Relative Yields for H to Non-resonant ΛΛ E522 data 1.0 μb/sr (Г H =0) Smeared with σ=5 MeV INC calculation results based on Ref (Y. Nara et al, NPA 614 (1997) 433)

18 TPC prototype test (RCNP-E384) σ=400 μm Tolerable with 10 7 Hz beam intensity. σ=400 μm obtained from the hits on 4-mm wide pads up to 10 6 Hz beam intensity.

19 Expected Momentum Resolutions

20 Mass Resolutions 1 MeV/c 2

21 H(2250) 0.2 μb/sr 1.0 μb/sr (Г H =0)

22 Lineshapes with respect to the H-decay width Г H Г H =0 MeV 1 MeV 3 MeV 5 MeV

23 H(2200) Λ p π H almost free from background in (K-,K+) reaction at 1.8 GeV/c.

24 Sensitivity Theoretical and Experimental Current UL at Λpπ threshold

25 Summary Theoretical and Experimental We plan to search for the H-dibaryon resonance in ΛΛ system and the bound one decaying weakly into Λpπ system at J-PARC. We plan to construct a hyperon spectrometer with a TPC to track Λ decays. We expect to collect 11K ΛΛ events for 100 shifts. We are going to get ready for physics runs late in 2014.